The present invention relates to an optical star-coupler for distributing and coupling light signals transmitted by waveguides such as optical fibers.
In order to build a communication network, using optical fibers or the like, optical star-couplers for distributing a light signal among plural optical fibers and coupling light signals from plural optical fibers into one optical fiber are necessary. A known optical star-coupler achieving this object is shown in FIG. 11.
This is fabricated by binding together plural optical fibers 101-105, melting the bundle at a high temperature to form a welded portion 110, and mounting a reflector 120 at the front end of the welded portion 110. As an example, a light beam going out of the optical fiber 103 passes through the welded portion 110, is reflected by the reflector 120, again passes through the welded portion 110, and is distributed to other optical fibers.
Generally, a light beam emerging from an optical fiber has an intensity distribution such that the intensity is high around the center of the beam, while decreasing toward the peripheral region of the beam. Therefore, in the optical star-coupler shown in FIG. 11, different areas of a light beam which emerges from a single optical fiber get distributed to other optical fibers, and so the light signals cannot be distributed uniformly. A light beam emerging from an optical fiber is propagated so as to become diffused. In the optical star-coupler constructed as shown in FIG. 11, the outgoing light beam is simply reflected by a reflector. Therefore, a large portion of the light beam does not reach other optical fibers and hence a large loss takes place.